2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * All advertising materials mentioning features or use of this software
36 * must display the following acknowledgement:
37 * This product includes software developed by Jeffrey M. Hsu.
39 * Copyright (c) 2001 Networks Associates Technologies, Inc.
40 * All rights reserved.
42 * This software was developed for the FreeBSD Project by Jonathan Lemon
43 * and NAI Labs, the Security Research Division of Network Associates, Inc.
44 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
45 * DARPA CHATS research program.
47 * Redistribution and use in source and binary forms, with or without
48 * modification, are permitted provided that the following conditions
50 * 1. Redistributions of source code must retain the above copyright
51 * notice, this list of conditions and the following disclaimer.
52 * 2. Redistributions in binary form must reproduce the above copyright
53 * notice, this list of conditions and the following disclaimer in the
54 * documentation and/or other materials provided with the distribution.
55 * 3. The name of the author may not be used to endorse or promote
56 * products derived from this software without specific prior written
59 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
71 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $
72 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.35 2008/11/22 11:03:35 sephe Exp $
75 #include "opt_inet6.h"
76 #include "opt_ipsec.h"
78 #include <sys/param.h>
79 #include <sys/systm.h>
80 #include <sys/kernel.h>
81 #include <sys/sysctl.h>
82 #include <sys/malloc.h>
85 #include <sys/proc.h> /* for proc0 declaration */
86 #include <sys/random.h>
87 #include <sys/socket.h>
88 #include <sys/socketvar.h>
89 #include <sys/in_cksum.h>
91 #include <sys/msgport2.h>
92 #include <net/netmsg2.h>
95 #include <net/route.h>
97 #include <netinet/in.h>
98 #include <netinet/in_systm.h>
99 #include <netinet/ip.h>
100 #include <netinet/in_var.h>
101 #include <netinet/in_pcb.h>
102 #include <netinet/ip_var.h>
103 #include <netinet/ip6.h>
105 #include <netinet/icmp6.h>
106 #include <netinet6/nd6.h>
108 #include <netinet6/ip6_var.h>
109 #include <netinet6/in6_pcb.h>
110 #include <netinet/tcp.h>
111 #include <netinet/tcp_fsm.h>
112 #include <netinet/tcp_seq.h>
113 #include <netinet/tcp_timer.h>
114 #include <netinet/tcp_timer2.h>
115 #include <netinet/tcp_var.h>
116 #include <netinet6/tcp6_var.h>
119 #include <netinet6/ipsec.h>
121 #include <netinet6/ipsec6.h>
123 #include <netproto/key/key.h>
127 #include <netproto/ipsec/ipsec.h>
129 #include <netproto/ipsec/ipsec6.h>
131 #include <netproto/ipsec/key.h>
133 #endif /*FAST_IPSEC*/
135 static int tcp_syncookies = 1;
136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
138 "Use TCP SYN cookies if the syncache overflows");
140 static void syncache_drop(struct syncache *, struct syncache_head *);
141 static void syncache_free(struct syncache *);
142 static void syncache_insert(struct syncache *, struct syncache_head *);
143 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
144 static int syncache_respond(struct syncache *, struct mbuf *);
145 static struct socket *syncache_socket(struct syncache *, struct socket *,
147 static void syncache_timer(void *);
148 static u_int32_t syncookie_generate(struct syncache *);
149 static struct syncache *syncookie_lookup(struct in_conninfo *,
150 struct tcphdr *, struct socket *);
153 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
154 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
155 * the odds are that the user has given up attempting to connect by then.
157 #define SYNCACHE_MAXREXMTS 3
159 /* Arbitrary values */
160 #define TCP_SYNCACHE_HASHSIZE 512
161 #define TCP_SYNCACHE_BUCKETLIMIT 30
163 struct netmsg_sc_timer {
164 struct netmsg nm_netmsg;
165 struct msgrec *nm_mrec; /* back pointer to containing msgrec */
169 struct netmsg_sc_timer msg;
170 lwkt_port_t port; /* constant after init */
171 int slot; /* constant after init */
174 static void syncache_timer_handler(netmsg_t);
176 struct tcp_syncache {
184 static struct tcp_syncache tcp_syncache;
186 TAILQ_HEAD(syncache_list, syncache);
188 struct tcp_syncache_percpu {
189 struct syncache_head *hashbase;
191 struct syncache_list timerq[SYNCACHE_MAXREXMTS + 1];
192 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
193 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1];
195 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU];
197 static struct lwkt_port syncache_null_rport;
199 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
201 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD,
202 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
204 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD,
205 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
209 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
210 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
213 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD,
214 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
216 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
217 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
219 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
221 #define SYNCACHE_HASH(inc, mask) \
222 ((tcp_syncache.hash_secret ^ \
223 (inc)->inc_faddr.s_addr ^ \
224 ((inc)->inc_faddr.s_addr >> 16) ^ \
225 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
227 #define SYNCACHE_HASH6(inc, mask) \
228 ((tcp_syncache.hash_secret ^ \
229 (inc)->inc6_faddr.s6_addr32[0] ^ \
230 (inc)->inc6_faddr.s6_addr32[3] ^ \
231 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
233 #define ENDPTS_EQ(a, b) ( \
234 (a)->ie_fport == (b)->ie_fport && \
235 (a)->ie_lport == (b)->ie_lport && \
236 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
237 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
240 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
243 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu,
244 struct syncache *sc, int slot)
246 sc->sc_rxtslot = slot;
247 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot];
248 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq);
249 if (!callout_active(&syncache_percpu->tt_timerq[slot])) {
250 callout_reset(&syncache_percpu->tt_timerq[slot],
251 TCPTV_RTOBASE * tcp_backoff[slot],
253 &syncache_percpu->mrec[slot]);
258 syncache_free(struct syncache *sc)
262 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
264 const boolean_t isipv6 = FALSE;
268 m_free(sc->sc_ipopts);
270 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt;
273 * If this is the only reference to a protocol-cloned
274 * route, remove it immediately.
276 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1)
277 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
278 rt_mask(rt), rt->rt_flags, NULL);
281 kfree(sc, M_SYNCACHE);
289 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
290 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
291 tcp_syncache.cache_limit =
292 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
293 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
294 tcp_syncache.hash_secret = karc4random();
296 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
297 &tcp_syncache.hashsize);
298 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
299 &tcp_syncache.cache_limit);
300 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
301 &tcp_syncache.bucket_limit);
302 if (!powerof2(tcp_syncache.hashsize)) {
303 kprintf("WARNING: syncache hash size is not a power of 2.\n");
304 tcp_syncache.hashsize = 512; /* safe default */
306 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
308 lwkt_initport_replyonly_null(&syncache_null_rport);
310 for (cpu = 0; cpu < ncpus2; cpu++) {
311 struct tcp_syncache_percpu *syncache_percpu;
313 syncache_percpu = &tcp_syncache_percpu[cpu];
314 /* Allocate the hash table. */
315 MALLOC(syncache_percpu->hashbase, struct syncache_head *,
316 tcp_syncache.hashsize * sizeof(struct syncache_head),
317 M_SYNCACHE, M_WAITOK);
319 /* Initialize the hash buckets. */
320 for (i = 0; i < tcp_syncache.hashsize; i++) {
321 struct syncache_head *bucket;
323 bucket = &syncache_percpu->hashbase[i];
324 TAILQ_INIT(&bucket->sch_bucket);
325 bucket->sch_length = 0;
328 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
329 /* Initialize the timer queues. */
330 TAILQ_INIT(&syncache_percpu->timerq[i]);
331 callout_init(&syncache_percpu->tt_timerq[i]);
333 syncache_percpu->mrec[i].slot = i;
334 syncache_percpu->mrec[i].port = tcp_cport(cpu);
335 syncache_percpu->mrec[i].msg.nm_mrec =
336 &syncache_percpu->mrec[i];
337 netmsg_init(&syncache_percpu->mrec[i].msg.nm_netmsg,
338 NULL, &syncache_null_rport,
339 0, syncache_timer_handler);
345 syncache_insert(struct syncache *sc, struct syncache_head *sch)
347 struct tcp_syncache_percpu *syncache_percpu;
348 struct syncache *sc2;
351 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
354 * Make sure that we don't overflow the per-bucket
355 * limit or the total cache size limit.
357 if (sch->sch_length >= tcp_syncache.bucket_limit) {
359 * The bucket is full, toss the oldest element.
361 sc2 = TAILQ_FIRST(&sch->sch_bucket);
362 sc2->sc_tp->ts_recent = ticks;
363 syncache_drop(sc2, sch);
364 tcpstat.tcps_sc_bucketoverflow++;
365 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) {
367 * The cache is full. Toss the oldest entry in the
368 * entire cache. This is the front entry in the
369 * first non-empty timer queue with the largest
372 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
373 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]);
374 while (sc2 && (sc2->sc_flags & SCF_MARKER))
375 sc2 = TAILQ_NEXT(sc2, sc_timerq);
379 sc2->sc_tp->ts_recent = ticks;
380 syncache_drop(sc2, NULL);
381 tcpstat.tcps_sc_cacheoverflow++;
384 /* Initialize the entry's timer. */
385 syncache_timeout(syncache_percpu, sc, 0);
387 /* Put it into the bucket. */
388 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
390 syncache_percpu->cache_count++;
391 tcpstat.tcps_sc_added++;
395 syncache_destroy(struct tcpcb *tp)
397 struct tcp_syncache_percpu *syncache_percpu;
398 struct syncache_head *bucket;
402 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
405 for (i = 0; i < tcp_syncache.hashsize; i++) {
406 bucket = &syncache_percpu->hashbase[i];
407 TAILQ_FOREACH(sc, &bucket->sch_bucket, sc_hash) {
408 if (sc->sc_tp == tp) {
410 tp->t_flags &= ~TF_SYNCACHE;
415 kprintf("Warning: delete stale syncache for tp=%p, sc=%p\n", tp, sc);
419 syncache_drop(struct syncache *sc, struct syncache_head *sch)
421 struct tcp_syncache_percpu *syncache_percpu;
423 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
425 const boolean_t isipv6 = FALSE;
428 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
432 sch = &syncache_percpu->hashbase[
433 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
435 sch = &syncache_percpu->hashbase[
436 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
440 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
442 syncache_percpu->cache_count--;
448 sc->sc_tp->t_flags &= ~TF_SYNCACHE;
453 * Remove the entry from the syncache timer/timeout queue. Note
454 * that we do not try to stop any running timer since we do not know
455 * whether the timer's message is in-transit or not. Since timeouts
456 * are fairly long, taking an unneeded callout does not detrimentally
457 * effect performance.
459 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq);
465 * Place a timeout message on the TCP thread's message queue.
466 * This routine runs in soft interrupt context.
468 * An invariant is for this routine to be called, the callout must
469 * have been active. Note that the callout is not deactivated until
470 * after the message has been processed in syncache_timer_handler() below.
473 syncache_timer(void *p)
475 struct netmsg_sc_timer *msg = p;
477 lwkt_sendmsg(msg->nm_mrec->port, &msg->nm_netmsg.nm_lmsg);
481 * Service a timer message queued by timer expiration.
482 * This routine runs in the TCP protocol thread.
484 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
485 * If we have retransmitted an entry the maximum number of times, expire it.
487 * When we finish processing timed-out entries, we restart the timer if there
488 * are any entries still on the queue and deactivate it otherwise. Only after
489 * a timer has been deactivated here can it be restarted by syncache_timeout().
492 syncache_timer_handler(netmsg_t netmsg)
494 struct tcp_syncache_percpu *syncache_percpu;
496 struct syncache marker;
497 struct syncache_list *list;
501 slot = ((struct netmsg_sc_timer *)netmsg)->nm_mrec->slot;
502 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
504 list = &syncache_percpu->timerq[slot];
507 * Use a marker to keep our place in the scan. syncache_drop()
508 * can block and cause any next pointer we cache to become stale.
510 marker.sc_flags = SCF_MARKER;
511 TAILQ_INSERT_HEAD(list, &marker, sc_timerq);
513 while ((sc = TAILQ_NEXT(&marker, sc_timerq)) != NULL) {
517 TAILQ_REMOVE(list, &marker, sc_timerq);
518 TAILQ_INSERT_AFTER(list, sc, &marker, sc_timerq);
520 if (sc->sc_flags & SCF_MARKER)
523 if (ticks < sc->sc_rxttime)
524 break; /* finished because timerq sorted by time */
525 if (sc->sc_tp == NULL) {
526 syncache_drop(sc, NULL);
527 tcpstat.tcps_sc_stale++;
530 inp = sc->sc_tp->t_inpcb;
531 if (slot == SYNCACHE_MAXREXMTS ||
532 slot >= tcp_syncache.rexmt_limit ||
534 inp->inp_gencnt != sc->sc_inp_gencnt) {
535 syncache_drop(sc, NULL);
536 tcpstat.tcps_sc_stale++;
540 * syncache_respond() may call back into the syncache to
541 * to modify another entry, so do not obtain the next
542 * entry on the timer chain until it has completed.
544 syncache_respond(sc, NULL);
545 tcpstat.tcps_sc_retransmitted++;
546 TAILQ_REMOVE(list, sc, sc_timerq);
547 syncache_timeout(syncache_percpu, sc, slot + 1);
549 TAILQ_REMOVE(list, &marker, sc_timerq);
552 callout_reset(&syncache_percpu->tt_timerq[slot],
553 sc->sc_rxttime - ticks, syncache_timer,
554 &syncache_percpu->mrec[slot]);
556 callout_deactivate(&syncache_percpu->tt_timerq[slot]);
558 lwkt_replymsg(&netmsg->nm_lmsg, 0);
562 * Find an entry in the syncache.
565 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
567 struct tcp_syncache_percpu *syncache_percpu;
569 struct syncache_head *sch;
571 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
573 if (inc->inc_isipv6) {
574 sch = &syncache_percpu->hashbase[
575 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
577 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
578 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
583 sch = &syncache_percpu->hashbase[
584 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
586 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
588 if (sc->sc_inc.inc_isipv6)
591 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
599 * This function is called when we get a RST for a
600 * non-existent connection, so that we can see if the
601 * connection is in the syn cache. If it is, zap it.
604 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
607 struct syncache_head *sch;
609 sc = syncache_lookup(inc, &sch);
614 * If the RST bit is set, check the sequence number to see
615 * if this is a valid reset segment.
617 * In all states except SYN-SENT, all reset (RST) segments
618 * are validated by checking their SEQ-fields. A reset is
619 * valid if its sequence number is in the window.
621 * The sequence number in the reset segment is normally an
622 * echo of our outgoing acknowlegement numbers, but some hosts
623 * send a reset with the sequence number at the rightmost edge
624 * of our receive window, and we have to handle this case.
626 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
627 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
628 syncache_drop(sc, sch);
629 tcpstat.tcps_sc_reset++;
634 syncache_badack(struct in_conninfo *inc)
637 struct syncache_head *sch;
639 sc = syncache_lookup(inc, &sch);
641 syncache_drop(sc, sch);
642 tcpstat.tcps_sc_badack++;
647 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
650 struct syncache_head *sch;
652 /* we are called at splnet() here */
653 sc = syncache_lookup(inc, &sch);
657 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
658 if (ntohl(th->th_seq) != sc->sc_iss)
662 * If we've rertransmitted 3 times and this is our second error,
663 * we remove the entry. Otherwise, we allow it to continue on.
664 * This prevents us from incorrectly nuking an entry during a
665 * spurious network outage.
669 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
670 sc->sc_flags |= SCF_UNREACH;
673 syncache_drop(sc, sch);
674 tcpstat.tcps_sc_unreach++;
678 * Build a new TCP socket structure from a syncache entry.
680 * This is called from the context of the SYN+ACK
682 static struct socket *
683 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
685 struct inpcb *inp = NULL, *linp;
690 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
692 const boolean_t isipv6 = FALSE;
696 * Ok, create the full blown connection, and set things up
697 * as they would have been set up if we had created the
698 * connection when the SYN arrived. If we can't create
699 * the connection, abort it.
701 so = sonewconn(lso, SS_ISCONNECTED);
704 * Drop the connection; we will send a RST if the peer
705 * retransmits the ACK,
707 tcpstat.tcps_listendrop++;
712 * Set the protocol processing port for the socket to the current
713 * port (that the connection came in on).
715 sosetport(so, &curthread->td_msgport);
718 * Insert new socket into hash list.
721 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
723 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
726 inp->inp_vflag &= ~INP_IPV6;
727 inp->inp_vflag |= INP_IPV4;
728 inp->inp_flags &= ~IN6P_IPV6_V6ONLY;
730 inp->inp_laddr = sc->sc_inc.inc_laddr;
732 inp->inp_lport = sc->sc_inc.inc_lport;
733 if (in_pcbinsporthash(inp) != 0) {
735 * Undo the assignments above if we failed to
736 * put the PCB on the hash lists.
739 inp->in6p_laddr = kin6addr_any;
741 inp->inp_laddr.s_addr = INADDR_ANY;
747 /* copy old policy into new socket's */
748 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp))
749 kprintf("syncache_expand: could not copy policy\n");
752 struct in6_addr laddr6;
753 struct sockaddr_in6 sin6;
755 * Inherit socket options from the listening socket.
756 * Note that in6p_inputopts are not (and should not be)
757 * copied, since it stores previously received options and is
758 * used to detect if each new option is different than the
759 * previous one and hence should be passed to a user.
760 * If we copied in6p_inputopts, a user would not be able to
761 * receive options just after calling the accept system call.
763 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS;
764 if (linp->in6p_outputopts)
765 inp->in6p_outputopts =
766 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT);
767 inp->in6p_route = sc->sc_route6;
768 sc->sc_route6.ro_rt = NULL;
770 sin6.sin6_family = AF_INET6;
771 sin6.sin6_len = sizeof sin6;
772 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
773 sin6.sin6_port = sc->sc_inc.inc_fport;
774 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
775 laddr6 = inp->in6p_laddr;
776 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
777 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
778 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) {
779 inp->in6p_laddr = laddr6;
783 struct in_addr laddr;
784 struct sockaddr_in sin;
786 inp->inp_options = ip_srcroute(m);
787 if (inp->inp_options == NULL) {
788 inp->inp_options = sc->sc_ipopts;
789 sc->sc_ipopts = NULL;
791 inp->inp_route = sc->sc_route;
792 sc->sc_route.ro_rt = NULL;
794 sin.sin_family = AF_INET;
795 sin.sin_len = sizeof sin;
796 sin.sin_addr = sc->sc_inc.inc_faddr;
797 sin.sin_port = sc->sc_inc.inc_fport;
798 bzero(sin.sin_zero, sizeof sin.sin_zero);
799 laddr = inp->inp_laddr;
800 if (inp->inp_laddr.s_addr == INADDR_ANY)
801 inp->inp_laddr = sc->sc_inc.inc_laddr;
802 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) {
803 inp->inp_laddr = laddr;
809 * The current port should be in the context of the SYN+ACK and
810 * so should match the tcp address port.
812 * XXX we may be running on the netisr thread instead of a tcp
813 * thread, in which case port will not match
814 * curthread->td_msgport.
817 port = tcp6_addrport();
819 port = tcp_addrport(inp->inp_faddr.s_addr, inp->inp_fport,
820 inp->inp_laddr.s_addr, inp->inp_lport);
822 /*KKASSERT(port == &curthread->td_msgport);*/
825 tp->t_state = TCPS_SYN_RECEIVED;
826 tp->iss = sc->sc_iss;
827 tp->irs = sc->sc_irs;
830 tp->snd_wl1 = sc->sc_irs;
831 tp->rcv_up = sc->sc_irs + 1;
832 tp->rcv_wnd = sc->sc_wnd;
833 tp->rcv_adv += tp->rcv_wnd;
835 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
836 if (sc->sc_flags & SCF_NOOPT)
837 tp->t_flags |= TF_NOOPT;
838 if (sc->sc_flags & SCF_WINSCALE) {
839 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE;
840 tp->requested_s_scale = sc->sc_requested_s_scale;
841 tp->request_r_scale = sc->sc_request_r_scale;
843 if (sc->sc_flags & SCF_TIMESTAMP) {
844 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP;
845 tp->ts_recent = sc->sc_tsrecent;
846 tp->ts_recent_age = ticks;
848 if (sc->sc_flags & SCF_SACK_PERMITTED)
849 tp->t_flags |= TF_SACK_PERMITTED;
851 tcp_mss(tp, sc->sc_peer_mss);
854 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
856 if (sc->sc_rxtslot != 0)
857 tp->snd_cwnd = tp->t_maxseg;
858 tcp_create_timermsg(tp, port);
859 tcp_callout_reset(tp, tp->tt_keep, tcp_keepinit, tcp_timer_keep);
861 tcpstat.tcps_accepts++;
871 * This function gets called when we receive an ACK for a
872 * socket in the LISTEN state. We look up the connection
873 * in the syncache, and if its there, we pull it out of
874 * the cache and turn it into a full-blown connection in
875 * the SYN-RECEIVED state.
878 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop,
882 struct syncache_head *sch;
885 sc = syncache_lookup(inc, &sch);
888 * There is no syncache entry, so see if this ACK is
889 * a returning syncookie. To do this, first:
890 * A. See if this socket has had a syncache entry dropped in
891 * the past. We don't want to accept a bogus syncookie
892 * if we've never received a SYN.
893 * B. check that the syncookie is valid. If it is, then
894 * cobble up a fake syncache entry, and return.
898 sc = syncookie_lookup(inc, th, *sop);
902 tcpstat.tcps_sc_recvcookie++;
906 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
908 if (th->th_ack != sc->sc_iss + 1)
911 so = syncache_socket(sc, *sop, m);
915 /* XXXjlemon check this - is this correct? */
916 tcp_respond(NULL, m, m, th,
917 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK);
919 m_freem(m); /* XXX only needed for above */
920 tcpstat.tcps_sc_aborted++;
922 tcpstat.tcps_sc_completed++;
927 syncache_drop(sc, sch);
933 * Given a LISTEN socket and an inbound SYN request, add
934 * this to the syn cache, and send back a segment:
935 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
938 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
939 * Doing so would require that we hold onto the data and deliver it
940 * to the application. However, if we are the target of a SYN-flood
941 * DoS attack, an attacker could send data which would eventually
942 * consume all available buffer space if it were ACKed. By not ACKing
943 * the data, we avoid this DoS scenario.
946 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
947 struct socket **sop, struct mbuf *m)
949 struct tcp_syncache_percpu *syncache_percpu;
952 struct syncache *sc = NULL;
953 struct syncache_head *sch;
954 struct mbuf *ipopts = NULL;
957 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
962 * Remember the IP options, if any.
965 if (!inc->inc_isipv6)
967 ipopts = ip_srcroute(m);
970 * See if we already have an entry for this connection.
971 * If we do, resend the SYN,ACK, and reset the retransmit timer.
974 * The syncache should be re-initialized with the contents
975 * of the new SYN which may have different options.
977 sc = syncache_lookup(inc, &sch);
979 tcpstat.tcps_sc_dupsyn++;
982 * If we were remembering a previous source route,
983 * forget it and use the new one we've been given.
986 m_free(sc->sc_ipopts);
987 sc->sc_ipopts = ipopts;
990 * Update timestamp if present.
992 if (sc->sc_flags & SCF_TIMESTAMP)
993 sc->sc_tsrecent = to->to_tsval;
995 /* Just update the TOF_SACK_PERMITTED for now. */
996 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
997 sc->sc_flags |= SCF_SACK_PERMITTED;
999 sc->sc_flags &= ~SCF_SACK_PERMITTED;
1002 * PCB may have changed, pick up new values.
1005 sc->sc_tp->t_flags &= ~TF_SYNCACHE;
1006 tp->t_flags |= TF_SYNCACHE;
1009 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
1010 if (syncache_respond(sc, m) == 0) {
1011 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot],
1013 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot);
1014 tcpstat.tcps_sndacks++;
1015 tcpstat.tcps_sndtotal++;
1022 * Fill in the syncache values.
1024 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO);
1025 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
1026 sc->sc_ipopts = ipopts;
1027 sc->sc_inc.inc_fport = inc->inc_fport;
1028 sc->sc_inc.inc_lport = inc->inc_lport;
1030 tp->t_flags |= TF_SYNCACHE;
1032 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1033 if (inc->inc_isipv6) {
1034 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1035 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1036 sc->sc_route6.ro_rt = NULL;
1040 sc->sc_inc.inc_faddr = inc->inc_faddr;
1041 sc->sc_inc.inc_laddr = inc->inc_laddr;
1042 sc->sc_route.ro_rt = NULL;
1044 sc->sc_irs = th->th_seq;
1046 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
1048 sc->sc_iss = syncookie_generate(sc);
1050 sc->sc_iss = karc4random();
1052 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */
1053 win = ssb_space(&so->so_rcv);
1055 win = imin(win, TCP_MAXWIN);
1058 if (tcp_do_rfc1323) {
1060 * A timestamp received in a SYN makes
1061 * it ok to send timestamp requests and replies.
1063 if (to->to_flags & TOF_TS) {
1064 sc->sc_tsrecent = to->to_tsval;
1065 sc->sc_flags |= SCF_TIMESTAMP;
1067 if (to->to_flags & TOF_SCALE) {
1068 int wscale = TCP_MIN_WINSHIFT;
1070 /* Compute proper scaling value from buffer space */
1071 while (wscale < TCP_MAX_WINSHIFT &&
1072 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) {
1075 sc->sc_request_r_scale = wscale;
1076 sc->sc_requested_s_scale = to->to_requested_s_scale;
1077 sc->sc_flags |= SCF_WINSCALE;
1080 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
1081 sc->sc_flags |= SCF_SACK_PERMITTED;
1082 if (tp->t_flags & TF_NOOPT)
1083 sc->sc_flags = SCF_NOOPT;
1085 if (syncache_respond(sc, m) == 0) {
1086 syncache_insert(sc, sch);
1087 tcpstat.tcps_sndacks++;
1088 tcpstat.tcps_sndtotal++;
1091 tcpstat.tcps_sc_dropped++;
1098 syncache_respond(struct syncache *sc, struct mbuf *m)
1102 u_int16_t tlen, hlen, mssopt;
1103 struct ip *ip = NULL;
1106 struct ip6_hdr *ip6 = NULL;
1108 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1110 const boolean_t isipv6 = FALSE;
1114 rt = tcp_rtlookup6(&sc->sc_inc);
1116 mssopt = rt->rt_ifp->if_mtu -
1117 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr));
1119 mssopt = tcp_v6mssdflt;
1120 hlen = sizeof(struct ip6_hdr);
1122 rt = tcp_rtlookup(&sc->sc_inc);
1124 mssopt = rt->rt_ifp->if_mtu -
1125 (sizeof(struct ip) + sizeof(struct tcphdr));
1127 mssopt = tcp_mssdflt;
1128 hlen = sizeof(struct ip);
1131 /* Compute the size of the TCP options. */
1132 if (sc->sc_flags & SCF_NOOPT) {
1135 optlen = TCPOLEN_MAXSEG +
1136 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1137 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1138 ((sc->sc_flags & SCF_SACK_PERMITTED) ?
1139 TCPOLEN_SACK_PERMITTED_ALIGNED : 0);
1141 tlen = hlen + sizeof(struct tcphdr) + optlen;
1145 * assume that the entire packet will fit in a header mbuf
1147 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1150 * XXX shouldn't this reuse the mbuf if possible ?
1151 * Create the IP+TCP header from scratch.
1156 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
1159 m->m_data += max_linkhdr;
1161 m->m_pkthdr.len = tlen;
1162 m->m_pkthdr.rcvif = NULL;
1165 ip6 = mtod(m, struct ip6_hdr *);
1166 ip6->ip6_vfc = IPV6_VERSION;
1167 ip6->ip6_nxt = IPPROTO_TCP;
1168 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1169 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1170 ip6->ip6_plen = htons(tlen - hlen);
1171 /* ip6_hlim is set after checksum */
1172 /* ip6_flow = ??? */
1174 th = (struct tcphdr *)(ip6 + 1);
1176 ip = mtod(m, struct ip *);
1177 ip->ip_v = IPVERSION;
1178 ip->ip_hl = sizeof(struct ip) >> 2;
1183 ip->ip_p = IPPROTO_TCP;
1184 ip->ip_src = sc->sc_inc.inc_laddr;
1185 ip->ip_dst = sc->sc_inc.inc_faddr;
1186 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */
1187 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */
1190 * See if we should do MTU discovery. Route lookups are
1191 * expensive, so we will only unset the DF bit if:
1193 * 1) path_mtu_discovery is disabled
1194 * 2) the SCF_UNREACH flag has been set
1196 if (path_mtu_discovery
1197 && ((sc->sc_flags & SCF_UNREACH) == 0)) {
1198 ip->ip_off |= IP_DF;
1201 th = (struct tcphdr *)(ip + 1);
1203 th->th_sport = sc->sc_inc.inc_lport;
1204 th->th_dport = sc->sc_inc.inc_fport;
1206 th->th_seq = htonl(sc->sc_iss);
1207 th->th_ack = htonl(sc->sc_irs + 1);
1208 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1210 th->th_flags = TH_SYN | TH_ACK;
1211 th->th_win = htons(sc->sc_wnd);
1214 /* Tack on the TCP options. */
1217 optp = (u_int8_t *)(th + 1);
1218 *optp++ = TCPOPT_MAXSEG;
1219 *optp++ = TCPOLEN_MAXSEG;
1220 *optp++ = (mssopt >> 8) & 0xff;
1221 *optp++ = mssopt & 0xff;
1223 if (sc->sc_flags & SCF_WINSCALE) {
1224 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1225 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1226 sc->sc_request_r_scale);
1230 if (sc->sc_flags & SCF_TIMESTAMP) {
1231 u_int32_t *lp = (u_int32_t *)(optp);
1233 /* Form timestamp option as shown in appendix A of RFC 1323. */
1234 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1235 *lp++ = htonl(ticks);
1236 *lp = htonl(sc->sc_tsrecent);
1237 optp += TCPOLEN_TSTAMP_APPA;
1240 if (sc->sc_flags & SCF_SACK_PERMITTED) {
1241 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
1242 optp += TCPOLEN_SACK_PERMITTED_ALIGNED;
1247 struct route_in6 *ro6 = &sc->sc_route6;
1250 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1251 ip6->ip6_hlim = in6_selecthlim(NULL,
1252 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
1253 error = ip6_output(m, NULL, ro6, 0, NULL, NULL,
1254 sc->sc_tp->t_inpcb);
1256 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1257 htons(tlen - hlen + IPPROTO_TCP));
1258 m->m_pkthdr.csum_flags = CSUM_TCP;
1259 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1260 error = ip_output(m, sc->sc_ipopts, &sc->sc_route,
1261 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb);
1269 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1271 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1273 * (A): peer mss index
1277 * The values below are chosen to minimize the size of the tcp_secret
1278 * table, as well as providing roughly a 16 second lifetime for the cookie.
1281 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1282 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1284 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1285 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1286 #define SYNCOOKIE_TIMEOUT \
1287 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1288 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1291 u_int32_t ts_secbits[4];
1293 } tcp_secret[SYNCOOKIE_NSECRETS];
1295 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1297 static MD5_CTX syn_ctx;
1299 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1302 u_int32_t laddr, faddr;
1303 u_int32_t secbits[4];
1304 u_int16_t lport, fport;
1308 CTASSERT(sizeof(struct md5_add) == 28);
1312 * Consider the problem of a recreated (and retransmitted) cookie. If the
1313 * original SYN was accepted, the connection is established. The second
1314 * SYN is inflight, and if it arrives with an ISN that falls within the
1315 * receive window, the connection is killed.
1317 * However, since cookies have other problems, this may not be worth
1322 syncookie_generate(struct syncache *sc)
1324 u_int32_t md5_buffer[4];
1329 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1331 const boolean_t isipv6 = FALSE;
1334 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1335 if (tcp_secret[idx].ts_expire < ticks) {
1336 for (i = 0; i < 4; i++)
1337 tcp_secret[idx].ts_secbits[i] = karc4random();
1338 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1340 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1341 if (tcp_msstab[data] <= sc->sc_peer_mss)
1343 data = (data << SYNCOOKIE_WNDBITS) | idx;
1344 data ^= sc->sc_irs; /* peer's iss */
1347 MD5Add(sc->sc_inc.inc6_laddr);
1348 MD5Add(sc->sc_inc.inc6_faddr);
1352 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1353 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1355 add.lport = sc->sc_inc.inc_lport;
1356 add.fport = sc->sc_inc.inc_fport;
1357 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1358 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1359 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1360 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1362 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1363 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1367 static struct syncache *
1368 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so)
1370 u_int32_t md5_buffer[4];
1371 struct syncache *sc;
1376 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1377 idx = data & SYNCOOKIE_WNDMASK;
1378 if (tcp_secret[idx].ts_expire < ticks ||
1379 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1383 if (inc->inc_isipv6) {
1384 MD5Add(inc->inc6_laddr);
1385 MD5Add(inc->inc6_faddr);
1391 add.laddr = inc->inc_laddr.s_addr;
1392 add.faddr = inc->inc_faddr.s_addr;
1394 add.lport = inc->inc_lport;
1395 add.fport = inc->inc_fport;
1396 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1397 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1398 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1399 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1401 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1402 data ^= md5_buffer[0];
1403 if (data & ~SYNCOOKIE_DATAMASK)
1405 data = data >> SYNCOOKIE_WNDBITS;
1408 * Fill in the syncache values.
1409 * XXX duplicate code from syncache_add
1411 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO);
1412 sc->sc_ipopts = NULL;
1413 sc->sc_inc.inc_fport = inc->inc_fport;
1414 sc->sc_inc.inc_lport = inc->inc_lport;
1416 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1417 if (inc->inc_isipv6) {
1418 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1419 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1420 sc->sc_route6.ro_rt = NULL;
1424 sc->sc_inc.inc_faddr = inc->inc_faddr;
1425 sc->sc_inc.inc_laddr = inc->inc_laddr;
1426 sc->sc_route.ro_rt = NULL;
1428 sc->sc_irs = th->th_seq - 1;
1429 sc->sc_iss = th->th_ack - 1;
1430 wnd = ssb_space(&so->so_rcv);
1432 wnd = imin(wnd, TCP_MAXWIN);
1436 sc->sc_peer_mss = tcp_msstab[data];